Hydrometallurgical leaching

ABSTRACT

A process and apparatus for hydrometallurgical leaching of unseparated, crushed mineral ores using a vessel having liquid stream forming nozzles in the lower portion thereof which operate to direct a stream of leaching liquid into solids in the lower portion of the vessel and to create a highly agitated interaction zone above which solids are settling under gravity and through which liquid from the lower portion rises upwardly in countercurrent flow. The vessel is sufficiently high that an overflow of low solids content liquid is taken from the top. Outlets, as for example discharge piping or sumps, are provided in the bottom of the vessel for the controlled removal of solids therefrom. In multistage operation, the solids content of the overflow liquid is removed and the liquid content of the underflow is removed and combined to yield a mineral pregnant liquor which serves as the leaching liquid for a preceding stage where less depleted solids are being processed. Solids removed from a stage are passed to a subsequent stage where less pregnant leaching solution is used, so that the solids not only are processed in each stage in counter-current flow to the leach solution, but the interstage progression of the solids and leaching liquid is also countercurrent. Single stage continuous operation is also disclosed in which solids having passed downwardly through the reactor are discharged periodically through a discharge trap formed in the lower portion of the vessel so as to minimize the amount of liquid discharged with the solids.

United States Patent 1 [111 3,885,017

Robinson et al. 7 45 M 20, 1975 HYDROMETALLURGICAL LEACHING [75]Inventors: Charles W. Robinson, San {57] ABSTRACT Francisco; Kenneth E,M -Mi A process and apparatus for hydrometallurgical leach- Tiburon, bth f C mi ing of unseparated, crushed mineral ores using a vessel havingliquid stream forming nozzles in the lower portion thereof which operateto direct a stream of leaching liquid into solids in the lower portionof the vessel [73] Assignee: Marcona Corporation, San

Francisco, Calif.

[22] Filed: Nov. 1, 1973 and to create a highly agitated interactionzone above which solids are settling under ravit and throu h [21] APPI-411,912 which liquid from the lower portiin risis upwardly in Rd d U S Ali i D counter-current flow. The vessel is sufficiently high [63]continuatiomimpan of Ser- No' 305,144, Nov. 9' that an overflow of lowsolids content liquid is taken 1972 abandone from the top. Outlets, asfor example discharge piping or sumps, are provided in the bottom of thevessel for [52] U5 CI H 423/1; 134/25 423/3]; the controlled removal ofsolids therefrom. In multi- 7 5/101 R stage operation, the solidscontent of the overflow liq- 5| Int. Cl C0lb COlc COld is removed andthe "quid underflm" C01 g C22!) is removed and combined to yield amineral pregnant 58 Field of Search 423/1, 23, 27, 31, 32, q whichServes as the leaching liquid for a p 423/4L 139, 23/267 3 267 p 267 R,ing stage where less depleted solids are being pro- 269' 270 R 75/101134/25 R cessed. Solids removed from a stage are passed to a subsequentstage where less pregnant leaching solu- [56] References Cited tion isused, so that the solids not only are processed UNITED STATES PATENTS ineach stage n counter-current flow to the leach solution, but theinterstage progression of the solids and [140,904 9/l9i7 Trent 23/27ileaching is also countepcurrent gl stage continuous operation is alsodisclosed in which solids having passed downwardly through the reactorare discharged periodically through a discharge trap formed in the lowerportion of the vessel so as to minimize the amount of liquid dischargedwith the solids.

Primary Examiner-Edward J. Meros Assistant Examiner-Eugene T. WheelockAttorney, Agent, or Firm-Flehr, Hohbach, Test,

Albritton & Herbert 9 Claims, 4 Drawing Figures smce 2 \I D SOLlDSSLURRY RECYCLE OVERFLOW RECYCLE la) n s s I- a U, Q E E To LEACHING someI SOLUTION STORAGE THICKENER 3a sewn RATOR PREGNANT LEACHING L'OUOR 5I05 SOLUTION FROM 1 HYDROMETALLURGICAL LEACHING This application is acontinuation-in-part of US. patent application Ser. No. 305,144, filedNov. 9, 1972, for I-IYDROMETALLURGICAL LEACI-IING now abandoned.

BACKGROUND OF THE INVENTION This invention relates to hydrometallurgicalleaching processes and apparatus and more particularly to the recoveryof copper or other metal values from ores by such leaching. Although theprocedures and apparatus to be disclosed herein are set forth withspecific reference to the hydrometallurgical leaching of copper ores,these same procedures and apparatus will be found applicable to othersimilar types or ores. Accordingly, the specific discussion of copperores herein should be taken as an illustration of the specificapplication of the invention to that case. But, the scope of theinvention should be taken more broadly, limited only by the scope of theappended claims.

In general, hydrometallurgical metal recovery processes includepreparation of the material, usually ore, dissolution of the values fromthe ore into solution, and subsequent recovery from solution by suitableprocedures. The dissolution step is commonly carried out as a leachingoperation; the most frequently used procedures being heap leaching,percolation leaching, or some form of agitation leaching. While leachingunder pressure or by bacterial action are also known, they are generallynot of interest in the present context.

In some circumstances, heap leaching finds use with low grade ore bodieshaving marginal economics but generally requires a long leaching cyclewhich may extend for months and a high consumption of leaching solvent.In percolation leaching in vats the ore is crushed to the size ofapproximately as inch top size, after which the ore is loaded into thevats and the leach solution percolated through the ore at apredetermined rate. In general, the ore in vat leaching remains instatic condition, and problems arise in attempting to reach highleaching efficiency due to excessive fines which develop duringbreakdown of the ore and which either block proper flow of the leachingsolution through the vat or cause channeling of the flow such that thesolution fails to reach such a large portion of the ore that extractionof all of the values becomes difficult if not impossible. Thus, whilevat leaching is reasonable in cost with respect to operation and capitaloutlay and does not contain undue grinding requirements, it neverthelessis not completely satisfactory due to poor recovery and long leachingtimes. In addition, the exhausted ore has to be mechanically removedfrom the vat usually with grab buckets, which results in a materialhandling problem each time the vat is unloaded and also results inmechanical damage to the vat and consequent high maintenance costs.

In addition to the foregoing, various types of agitation leaching havebeen used particularly for fine materials obtained either fromseparation from crushed ores used in vat leaching or by additionalgrinding. Agitation is carried out either using mechanical agitatorswhere the energy of mixing is supplied by a rotary shaft coupled to animpeller or raker arm, or the so-called Pachuca agitator, in which theagitation is supplied by an air lift rising through a slurry pulp of theore and leaching solution. In order for either of these agitationsystems to work properly, the additional grinding must be carried out tobetween minus 10 to minus 48 mesh. Agitation leaching of this sizematerial does provide for high metal recovery rates; however, thecapital cost and cost of operation of such a combination may be high,and requires high preparation costs associated with ore grinding andseparation. Furthermore, there is a size range between the coarsematerial used in vat leaching and the finely ground material used inagitation leaching for which no really satisfactory leaching systemexists.

In view of the above limitations and disadvantages there is a need foran improved process and apparatus for hydrometallurgical leaching.

SUMMARY OF THE INVENTION AND OBJECTS In general, it is an object of thepresent invention to provide a process and apparatus forhydrometallurgical leaching which will overcome the above limitationsand disadvantages, and which particularly is operable to solve theproblem of material handling created by the movement of the solid phase,both during the leaching operation and when exhausted, and whichsimultaneously provides this advantage while eliminating the requirementof high grinding costs and coarse and fine fractional separation.

Another object of the invention is to provide a pro- I cess andapparatus of the above character in which the ore preparation requiresonly crushing to about inch top size, such crushed ore requiring nofurther grinding or separation, and which provides recovery efficienciescomparable to those obtained in agitation leaching. In addition, the useof crushed ore of lower top size results in the ability to form apumpable slurry which is readily handleable by the techniques disclosedherein and also by commonly available slurry handling equipment.

A further object of the present invention is to provide a process andapparatus for the leaching of ores which is adaptable to either singlestage or multiple stage operation, which will readily accept relativelycoarse material as well as fines so that the leaching can beaccomplished in a single system, which is inherently immune to clogging.

A further object is to provide a process and apparatus of the abovecharacter which also makes use of the leaching liquid injectionapparatus to provide for selective removal of the solids from the vesseleither continuously or in batches.

Another object of the invention is to provide the process and apparatusfor hydrometallurgical leaching which is essentially uncloggable andwhich maintains the solid phase and the liquid phase in constant motionand further in which forcible contact of the liquid phase with the solidphase is accomplished in an agitation zone having continuous intermixingand redistribution of the solids in an incoming stream of the liquidphase.

Another object of the hydrometallurgical process and apparatus of thepresent invention is to minimize capital costs for the leachingequipment while maintaining a high percentage recovery of the desiredvalue and further in which the cycle time for leaching of coarser solidsis substantially reduced.

Another object of the invention is to provide a hydrometallurgicalprocess and apparatus of the above character which lends itself tomultistage operation each stage of which is substantially similar to andthereby interchangeable with the succeeding or preceding stage wherebycycling of leaching liquid alone between the stages effectively causestransfer of the solids between stages without the need for physicalmovement of solids from one place to another.

Another object of the invention is to provide an improvedhydrometallurgical leaching process and apparatus of the above characterwhich eliminates the need for direct mechanical agitation such as rakearms or impellers, and which does not place requirements for coarse andfine separation on the material size used and accordingly is capable ofoperating as a single reactor and complete processing stage, acceptingsuitably crushed ore.

Another object of the invention is to provide a hydrometallurgicalprocess and apparatus which achieves a high degree of agitation andintermixing of the leaching liquid with an ore solids phase using a highenergy liquid jet.

Another object of the invention is to provide a closed system forrecycling of the leaching solution and which allows for heating of thesolution for addition of mineral content to the solution, as for examplethe addition of sodium chloride, or the addition or replenishment ofoxidizing agents which could assist in accelerating the leachingprocess.

Another object of the invention is to provide a hydrometallurgicalprocess and apparatus of the above character in which the solids flowthrough and residence time is determined by the controlled periodicdischarge of predetermined quantities of solids.

Another object of the invention is to provide a hydrometallurgicalprocess and apparatus fo the above character in which a gas volume isintroduced into the lower portion of the reactor vessel, usuallyperiodically, to obtain addition disturbance and agitation of thecontained bed of material.

In general, the foregoing objects are achieved by providing a processand apparatus using a large upright vessel having side walls and abottom wall. Solids discharge outlets are formed in the bottom wall.Means are provided for supplying a leaching liquid in a stream orstreams directed generally parallel to and above the bottom wall of thevessel. The stream or streams are progressively traversed as by rotationor oscillation to sweep over the bottom of the vessel and create ahighly agitated reaction zone in the lower region thereof. Ore solidsare crushed to a top size of about inch and are introduced withoutfurther grinding or separation at the top of the vessel to move undergravity, and pass counter-current to a generally upward flow of leachingliquid. As the solids enter the lowermost region of the vessel, they areimpacted by the streams and are brought into a highly agitated state.Solids are withdrawn from the lower region of the vessel after havingpassed therethrough and either may be recycled in the same stage ortaken to subsequent stages if multi-stage operation is utilized. If themineral recovery is satisfactory, the solids can be passed immediatelyto a washing stage. Leaching liquid, now pregnant, is removed from thetop of the treatment vessel and is either recycled, taken to thepreceding stage in interstage countercurrent flow with respect to thesolids if multi-stage operation is used, or processed to recover thecontained values. In one preferred form of the present invention, thevessel is provided with a discharge trap which facilitates theaccummulation of solids with a minimum amount of liquid for periodicdischarge from the vessel.

The frequency of discharge of solids determines the residence time ofthe solids in passing through the vessel. In addition, provision is alsomade for the introduction of quantity of gas, usually air, as a bubblewhich passes upwardly through the bed of solids and liquid to promotefurther agitation of the bed when in the vessel. These and other objectsand features of the invention will become apparent from the followingdetailed description when taken in conjunction with the accompanyingdrawings which relate both to multiple and single stage arrangements forcarrying out the present invention.

FIG. 1 is a schematic diagram of a hydrometallurgical apparatusconstructed and adapted in accordance with the present invention.

FIG. 2 is a schematic illustration of a stage of a hydrometallurgicalleaching process and apparatus for carrying out the present invention.

FIG. 3 is a schematic view in cross-section of a continuously operatingsingle stage form of leaching apparatus constructed in accordance withthe present invention.

FIG. 4 is a cross-sectional view taken along the lines 25 44 of FIG. 3.

Referring to FIGS. 1 and 2, there is shown a single stage of apparatusfor carrying out the procedure of the present invention. It should beunderstood that preceding and subsequent stages substantially identicalto the single stage illustrated in FIG. 2 may be connected therewith inseries such that liquid and solids movement proceeds from stage to stagein counter-current flow as will be described. Since each stage issubstantially the same and for the sake of clarity of presentation, thedescription herein is set forth by illustration of a single stage and bygeneral reference to preceding and succeeding stages. It is a feature ofthe present invention that it is adaptable for use either in multi-stageoperation if required for satisfactory and economical processing of theore, or in single stage operation.

Solids suitable for use in the present invention should be sized, groundor crushed to about inch top size. In general, this will require onlyknown ore crushing procedures and no grinding will be required. Grindingcontemplates reduction for example to l0 mesh or lower and requires arod or ball mill in usual practice. This grinding to such a small sizeand its costs can be eliminated by the present invention.

The ore passed through such size reduction is now sufficientlysubdivided and is ready to be used without any separation steps; for,all ore sizes from inch to fines can be processed in the reactordisclosed herein.

Each stage includes a reactor vessel in which the leaching action takesplace. The crushed solids are introduced at an input 12 arranged at theupper end 14 or top of the vessel while the leach liquor is introducedinto the lower portion 16 of the vessel so that the leaching liquorcreates a column which is gradually rising through the vessel andeventually overflowing while solids settle downwardly under gravity andgenerally pass from the top to the bottom of the vessel. The vessel isformed with side walls 18 and a bottom wall 20. Means is provided forforming a sump 22 in the bottom wall, together with a jet nozzle 24 forsupplying leaching liquid under high velocity in a stream directedgenerally parallel to and over the bottom wall from a position above thesump. A pump 26 is provided for receiving leaching solution from asource such as generally indicated at 28.

While the vessel shown herein shows an arrangement using a horizontalbottom wall and horizontally directed jet stream, it should beappreciated that a conically sloped bottom wall of the vessel could beused and that the jet would then have to be directed upwardly at thesame angle and somewhat above the bottom wall level. In this positionthe stream is still directed generally parallel to the bottom wall eventhough the latter is sloped. Accordingly, the phrases-generally parallelto the bottom wall,-substantially horizontal, or-at a substantial angleto the verticalas used herein and in the claims should be interpreted ascomprehending a reasonable range of directions as well as the horizontallimit discloses for the purpose of illustration. It is not expected thatthis range will exceed 45, at the other limit.

A suitable drive system 30 is arranged with respect to the liquid forcarrying the liquid jet nozzle and for rotating the same so that theliquid jet is progressively moved over the bottom of the vessel and thestream therefrom is swept through an arc. Suitable piping 32 carries theunderflow from the sump to a liquid-solid separator indicated at 34.Means is provided for forming a wier 39 at the top of the vessel fortaking overflow liquid which is passed to a thickener 36 which removessolids and delivers the resultant pregnant solution at 38. Leachingliquor recovered from the underflow is also taken from separator 34 topregnant solution storage 38.

The wier 39 is formed at the entire periphery of the top edge of thevessel and includes a collection through 40 which surrounds the top ofthe vessel and slopes and drains into an outlet pipe 41. By using theentire periphery of the vessel the height of flow over the wier isreduced to a minimum and higher solids separation efficiencies areobtained.

The vessel is constructed in an upright configuration of preferablycircular cross section having a height sufficient to permit thedevelopment of essentially three zones within the vessel as will bedescribed. At this point it will be helpful to recall that the usualsettling of solids phase from a liquid phase results in three generalzones: the compacted, lower zone; above this a zone of hindered settlingin which particles are in contact a certain amount of time; and abovethe hindered settling zone, a zone of free settling in which particlesare not in sufficient contact to be a factor. In the present invention,formation of the lower compacted zone is prevented and that same regionis developed into a highly agitated zone as will be more fullydescribed.

In this connection, the present invention possesses a significantadvantage in that start-up, or restart from shut-down is effected by theoperation of the jet itself and is accordingly a single and easyprocedure. This is in contrast to normal mechanical agitation leachingsystems where start-up, especially after shut-down during operationoften involves the expenditure of considerable time and expense.

Assuming that the vessel is initially loaded with an appropriatequantity of ore pulp, operation proceeds by introducing the leachingsolution through the nozzle 34 as a high-velocity jet stream indicatedat 44. This stream progressively moves through the solids in thelowermost portion of the vessel about an axis of rotation as to sweepout a generally circular path lying in a substantially horizontal plane.This causes the development in the lowermost region of the vessel of ahighly agitated reaction zone 46 in which constant intermixing andforcible contact between the leaching liquid and the solids within thatzone takes place. The degree of agitation produced in the zone issufficiently high that constant redistribution of solids in the zonetakes place without any accumulation of settled solids. As additionalleaching liquid is introduced, the liquid stream rises generally as acolumn indicated by arrows 50 and passes from the agitation zone andthrough the solids above that zone until overflow through the wier 39takes place. The height of the vessel is such that the zone 52 above theagitation zone operates with counter-current flow of the leaching liquidpercolating upwardly through settling solids 54. Above these is a thirdzone 56 which the leaching liquid gradually clarifies and reaches theoverflow. Thus, the vessel can be generally characterized as providingcounter-current movement of a column of solids with relation to a risingcolumn of leaching solution, the solution being injected in a highvelocity stream creating constant agitation in the lowermost zone 46above which the solids are progressively more settled with the generalpercolation of the leaching solution through the solids. Above the Isolids zone 52 is essentially liquid from which solids have settled and,the liquid being pregnant from the effective leaching.

In addition to the foregoing description of the various zones in thevessel, certain additional features are found when operating inaccordance with the present invention. In general, the coarse materialssettle faster in the counter-current stream of leaching liquid while thefine material settles somewhat more slowly. Therefore, the residencetime of the fines in passing through the leaching liquid is somewhatgreater than that of the coarser material. Depending on the leachingliquid flow rate, some of the fines may not settle at all and willoverflow or travel upwardly with the leaching liquid. Where the flowrate is sufficiently high, the character of the fines can be such thatthey do not settle readily. However, the amount of residence timerequired to extract the values from the ore solids is inversely relatedto their size so that the fines need only spend a short residence timein the vessel whereas the coarser materials should spend the longest.Accordingly, it is often found that the settling rates of certainmaterials in the rising leaching solution corresponds with the requiredresidence time. For this reason, in certain situations, the fines whichoverflow with the leaching liquid may be discarded after being passedthrough a thickener for recovery of the liquor, and the upward flow rateof leaching liquid can often be adjusted to maintain an adequateresidence time for the finer materials.

in other situations, this natural classification may have the oppositeeffect and be undesired, that is to say, the fact that the larger sizepieces settle downwardly at a faster rate than the smaller size piecesresults in those fines with low but positive settling rates spending alonger residence time in the reactor than the larger pieces.Furthermore, discharge of any of the solids from the top of the reactorvessel necessitate additional solids liquid separation of the overflowwhich in many cases is not desired. Thus, the natural classification cantend to work against the desired results since the larger pieces whichrequire the longer treatment time settle and are withdrawn before thedesired treatment has been completed. In this situation, removal of thesolids from the lower portion of the vessel and recirculation of themthrough the vessel by reintroducing them at the top will permit thesolids to receive sufficient treatment. In addition, the existing loadof solids and fines already in the vessel will cause the solids beingrecirculated to spend an even longer second pass residence due to beingimpeded in settling by the solids already present. In either case, anddepending upon the nature of the distribution of sizes of the solidsbeing processed, it is possible to effect satisfactory leachingresidence times for the various solids fractions, either with theassistance of the natural settling and classification of the solids asthey pass through the reactor or if this is adverse, by the employmentof suitable recirculation of the larger solids.

The solids within the vessel are removed either periodically orcontinuously through the sump 22 by the opening of a suitable valve 57.The nature of the reaction of the jet nozzle in maintaining the lowerhighly agitated slurry zone within the vessel is such that thewithdrawal of solids as an underflowing slurry is rapid and effectiveunder all conditions. Solids removed are either passed to the next orsucceeding stage after being passed through the separator 34 to recoverpregnant leaching liquid, the succeeding stage possessing leachingliquid of less pregnant character. If the solids are exhausted they canbe sent to tailings.

The overflow of pregnant leach solution is passed through thickener 36to remove any entrained solids and is then either passed to metal valuerecovery extraction or to an adjacent stage to react with solids whichare less depleted.

During the operation of each stage illustrated it may be desirable toeither pass a portion or all of the overflow back through aproportioning valve 58 and the jet nozzle or directly into peripherallocations located in the lower portion of the vessel as through overflowrecycling line and valve 60.

In some circumstances, recycling of the solids in the same vessel may bedesired, in which case this is easily accomplished by returningunderflow solids withdrawn from the sump as a slurry to the uppermostportion of the vessel through slurry recycle line and valve 62. Such aprocedure will ensure circulation of the solids, particularly if thesolids are being batch processed with respect to that stage.

An example of the use of the present invention will now be given:

A typical oxide copper ore bearing 0.7% copper oxides was crushed in acone crusher to 36 inch. A quantity of this ore was introduced into thereactor vessel by pumping the same as an aqueous slurry and draining offthe entraining water. Lixivant of 6% H 80 was jetted into the lowerregion of the vessel. This acid rose upwardly through the solids formingan overflow which was passed through the thickener and the liquid phasereturned through the jet nozzle. These operations were continued forabout three hours, at the end of which copper recovery by leaching wasabout 90% complete and the pregnant liquor was suitable for furtherprocessing.

The pregnant liquor was then drained off, the solids washed, as withwater, to remove any residual values. Thereafter, the solids weredischarged as a slurry by the operation of the jet mechanism using wateras the liquid entraining phase.

In the foregoing example, it will be noticed that the solids, afterleaching is completed, were removed in a water suspension as a slurry.Like the leaching operation itself, this procedure is carried out underflooded conditions in which the high velocity jet stream works into thesolids in the lowermost region of the vessel. The solids impacted by thestream are repulped by it and drain back to the sump as a dischargeableslurry. By progressively moving the jet, new solids are continuallybeing impacted and removed until the material in the lowermost region isreduced to less than that which will support the weight of the solidsabove. The entire load then shifts downwardly to be removed in turn.

Referring now to FIGS. 3 and 4 there is shown another embodiment ofleaching apparatus constructed in accordance with the present inventionand which provides for particularly simplified solids feed throughoperation as well as periodic solids removal in a controlled manner toregulate solids residence time as well as providing for the intermittentintroduction of an agitating gas stream into the lower region of thereactor. Thus, as shown, there is provided a vessel 100 having sidewalls 102 and a bottom wall 104. Means are provided for choke feedingsolids into the reactor and consists of the hopper 106 which passesthrough a chute 108 downwardly into the uper region of the vessel.Solids are thereby introduced into the vessel up to the lower end of thechute 108, and as solids level is lowered additional solids areautomatically fed by gravity so as to maintain the upper height ofsolids at the level established by the lower end of the chute.

Means are provided for intermittently removing solids from the vesseland consists of discharge traps 110, 112, and 114. Each of the trapsconsists of an upper valve 116 and a lower valve 118 interconnected by adischarge volume determining pipe section 120. The outlets of each ofthe lower valves 118 are passed to either a succeeding leaching stage,or, preferably if single stage operation can be effected, to the solidsinput hopper 124 of a washing stage 126. Each valve is of a suitabletype as for example a pinch valve consisting of a housing containing asleeve of elastomeric material therein which is compressed by externaland pneumatic pressure so as to close the valves. Such valves areavailable from the Clarkson Company of California.

In operation, controls associated with the valves permit the sequentialopening and closing thereof so that when the first valve is openedsolids from the reactor empty into the pipe section and first valve. Thepipe section 110 thus defines a solids discharge volume. Subsequently,the first valve is closed and the second valve opened to therebyintermittently discharge an amount of material from the lower region ofthe reactor. It is found that with an open air access available to thesecond valve that after discharge the volume defining pipe section isfilled with air and upon repetition of the cycle closing the secondvalve and opening the first valve, this air volume is introduced intothe bottom region of the reactor as a gas bubble which purges uswardlythrough the vessel and thereby work the bed so as to further preventchanneling within the contained material. Accordingly, the dischargetraps also serve as means for periodically introducing a gas bubble intothe lower region of the vessel.

Means are provided for introducing leaching liquid into the lower regionof the vessel 100 and consists of a plenum chamber type upstandingnozzle 130. In addition, to provide for greater scope of coverage, othernozzles 132, 133 and 134 are positioned about the periphery of thevessel. Means are provided for oscillating or rotating each of thenozzles to sweep out an are over the bottom of the vessel. As theleaching liquid is introduced, the entire lower region of the vessel upto the height determined by the height of the uppermost ones of thenozzles is turned into an agitated reaction zone wherein the solids arevigorously intermixed with the incoming leaching liquid. For clean uppurposes, a sump 150 may also be provided in the lower region of thevessel in a manner similar to that set forth with respect to theapparatus shown in FIGS. 1 and 2, so that the vessel may be emptied fromtime to time.

The washing stage I26 is similarly constructed to the leaching stage.Thus, there is provided nozzle means 136 for introducing a washingliquid, usually water, into the lower region of a vessel 138 so as tocreate an agitated zone in the bottom of the vessel and therebyfacilitate release of metal values from the solids by washing action.The input feed hopper 124 automatically choke feeds material from theprior stage into the vessel through a chute 125 in the same manner asthat described with respect to vessel 100 and chute 108. Outlets 140,142 are provided in the bottom wall of the washing vessel and areconstructed in the same manner as the solids discharge traps 110, 112,I14 previously described. The output of the solids discharge traps ispassed to a suitable slurry pump with sufficient make up water tofacilitate rapid handling of the exhausted solids.

The operation of the apparatus of FIGS. 3 and 4 will now be described ingreater detail. Let it be assumed that leaching liquid in an appropriatequantity is being introduced into the lower region of the vessel andthat solids have been introduced through the hopper 106 and chute 108 toa predetermined height within the vessel. As additional leaching liquidis introduced, the liquid creates a vigorously agitated zone in thelower region of the vessel in which solids that have been movingdownwardly are vigorously contacted by the incoming leaching liquidstreams. The entire flow of material through the reactor iscounter-current, the pregnant leaching liquid ultimately rising to thetop passing out the overflow wier 148. The pregnant liquid may then betreated in the same manner as in the apparatus of FIG. 2.

Periodically, the discharge traps are operated to take on a load ofsolids by the opening of the upper valve while maintaining the lowervalve closed. Solids preferentially fill the trap displacing essentiallyall the liquid except for that contained in the interstices. The uppervalve is then closed and the lower valve opened to discharge apredetermined quantity of solids. As the solids are taken into thedischarge trap, a gradual movement of the entire bed contained withinthe reactor takes place. In general, the maintenance of a high degree ofmovement of the material within the reactor is achieved by a combinationof the working of the material due to periodic withdrawal of solids fromthe bottom as well as the surge created by the traversing jet streamsmoving about in the lower region of the vessel.

The foregoing primary forces are aided, in addition, by the introductionof a gas bubble, usually air, during each cycle of operation of thedischarge traps. This rising gas passes through the bed of material andmoves the material sufficiently to prevent channeling of liquid pathsthrough the bed. In this way, there is provided in the disclosedapparatus a means for a controlled selective withdrawal of essentiallysolids from the bottom of the reactor while maintaining an uppercounter-current flow of leaching liquid. It is believed that the solidscontent of material removed from the lower region of the vessel can bemaintained at such a high level that the loss of leaching liquidsimultaneously with the dis charge of solids will not be an appreciablefactor. The residence time of the solids passed through the reactor iscontrolled by the rate of operation and defined volume of the dischargetraps.

In general, the operation of the reactor as disclosed is exceedinglysimple with respect to solids handling inasmuch as the feed is bygravity and is automatic without moving parts. The valves utilized inthe discharge traps are reliable and simple to operate and provide totalcontrol of the solids movement rate. It should also be pointed out thatthe leaching liquid circuit can be maintained in a closed circuit so asto avoid environmental impact and also permit the controlledmodification of the leaching liquid to optimum conditions. This includesthe possibility of heating or of adding oxidizing agents to thelixiviant.

While the operation of the apparatus of FIGS. 3 and 4 is similar to thatof FIG. 2, there are important differences. For, by having theparticular feed arrangement disclosed, the reactor is divided into onlytwo zones; the lower agitated zone, and an overlying zone ofsolids-in-contact slowly moving downwardly toward the agitated zone.Thus, the free-settling zone of the apparatus has been eliminated whileobtaining the added feature of an automatic, non-mechanical solids feedarrangement. While there has been disclosed particular forms of theinvention which are believed suitable for carrying out the presentinvention, it should be understood that many modifications andvariations can be made to the disclosed apparatus without departing fromthe spirit and scope of the present invention. For example, thedischarge traps of the appartus shown by FIGS. 3 and 4 also providesmeans for introducing gas bubbles into the lower regions of the reactor.Such means could easily be separately provided if desired. Furthermore,while there has been shown herein apparatus having bottom mounted jetstream nozzles, it should be understood that the actual mountingarrangement can be varied, as for example by mounting the entire nozzleas a removable or fixed structure suspended from the top of the vesseland extending downwardly into the lower region. Accordingly, the scopeof the present invention should be taken generally in accordance withthe scope of the following claims and without specific reference to theparticular features disclosed by way of example herein.

What is claimed is:

l. A method for leaching the extractable mineral values from an orehaving particulate form using a reactor vessel in which ore and aleaching liquid are simultaneously placed in contact, comprising thesteps of introducing the ore into the upper region of the reactor vesseland simultaneously introducing the extracting liquid into a lowermostregion of the vessel such that the solids gradually move as asolids-in-contact bed downwardly under gravity through a rising columnof extracting liquid to provide counter-current extraction of the valuesfrom said ore, and further comprising the steps of directing theextracting liquid as a rotating agitatin g stream in a region generallyparallel to and above the bottom wall of said vessel, progressivelymoving said stream about said lower region at a speed sufficient tocause the development of a highly agitated reaction zone in said lowerregion, the agitation being sufficiently great that constant intermixingand recontact is obtained between the liquid and the solids in saidzone, simultaneously withdrawing a liquid overflow stream from the upperregion and withdrawing solids as underflow from said lower region ofsaid vessel and, controlling the rate of solids withdrawal so that asubstantial predetermined height of solids introduced into the vessel ismaintained in an overlying zone of solids-incontact, said overlying zonegradually moves downwardly toward and then through said agitation zoneat a rate controlled by said solids withdrawal rate, said overlying zonebeing in contact with said agitation zone.

2. The method of claim 1 further including crushing the ore to top sizeof about inch and supplying the ore so crushed for introduction to thevessel without further subdivision or classification.

3. The method of claim 1 further including the steps of removing theleaching liquor from said vessel after recovery of the values, washingthe solids to recover the residual leaching liquor, subsequentlyremoving the washed solids by introducing a liquid as a high velocityjet stream in the lowermost region in the vessel to thereby pulp thesolids into a pumpable slurry, and continuously removing said slurry asformed from the vessel.

4. The method of claim 1 further including the steps of removing theleaching liquid from the vessel when the mineral values have beenrecovered to leave at least partially depleted solids in the vessel, andsubsequently removing the solids by directing a liquid jet stream intothe lowermost region of the vessel and progressively moving said jetstream, the impact of the stream causing formation of a flowable slurryof said solids, and simultaneously removing freshly formed slurrycontinuously through the bottom of said vessel.

5. The method of claim 1 further including the additional steps ofperiodically withdrawing a quantity of solids from the bottom of saidreactor with a minimum of liquid and periodically introducing a quantityof gas into the bottom region of said reactor, said gas rising upwardlythrough said vessel to thereby agitate the bed of material containedtherein.

6. The method of claim 1 in which the height of said continuous solidsbed is maintained at a predetermined level so that the bed fills themajor portion of the reaction vessel.

7. The method of claim 6 together with the step of automaticallycontrolling the height at said predetermined level by providing anoverlying ore supply with gravity feed and choking said supply at saidlevel.

8. The method of claim 1 in which the rotating agitating stream sweepsprogressively radially outwardly from a vertical axis.

9. The method of claim 6 in which the rate of solids withdrawal iscontrolled by use of a discharge volume determining pipe having an inletvalve and outlet valve, comprising the additional steps of opening saidinlet valve with said outlet valve in a closed position to load saidpipe section, subsequently closing said inlet valve and opening saidoutlet valve to discharge a predetermined quantity of solids, andrepeating said additional steps in sequence to periodically fill andempty the pipe section.

I i i It

1. A METHOD FOR LEACHING THE EXTRACTABLE MINERAL VALUES FROM AN OREHAVING PARTICULATE FORM USING A REACTORVESSEL IN WHICH ORE AND ALEACHING LIQUID ARE SIMULTANEOUSLY PLACED IN CONTACT, COMPRISING THESTEPS OF INTRODUCING THE ORE INTO THE UPPER REGION OF THE REACTOR VESSELAND SIMULTANEOUSLY INTRODUCING THE EXTRACTING LIQUID INTO A LOWERMOSTREGION OF THE VESSEL SUCH THAT THE SOLIDS GRADUALLY MOVE AS ASOLIDS-INCONTACT BED DOWNWARDLY UNDER GRAVITY THROUGH A RISING COLUMN OFEXTRACTING LIQUID TO PROVIDE COUNTER-CURRENT EXTRACTION OF THE VALUESFROM SAID ORE, AND FURTHER COMPRISING THE STEPS OF DIRECTING THEEXTRACTING LIQUID AS A ROTATING AGITATING STREAM IN A REGION GENERALLYPARALLEL TO AND ABOVE THE BOTTOM WALL OF SAID VESSEL, PROGRESSIVELYMOVING SAID STREAM ABOUT SAID LOWER REGION AT A SPEED SUFFICIENT TOCAUSE THE DEVELOPMENT OF A HIGHLY AGITATED REACTION ZONE IN SAID LOWERREGION, THE AGITATION BEING SUFFICIENTLY GREAT THAT CONSTANT INTERMIXINGAND RECONTACT IS OBTAINED BETWEEN THE LIQUID AND THE SOLIDS IN SAIDZONE, SIMULTANEOUSLY WITHDRAWING A LIQUID OVERFLOW STREAM FROM THE UPPERREGION AND WITHDRAWING SOLIDS AS UNDERFLOW FROM SAID LOWER REGION OFSAID VESSEL AND, CONTROLLING THE RATE OF SOLIDS WITHDRAWAL SO THAT ASUBSTANTIAL PREDETERMINED HEIGHT OF SOLIDS INTRODUCED INTO THE VESSEL ISMAINTAINED IN AN OVERLYING ZONE OF SOLIDS-IN-CONTACT, SAID OVERLYINGZONE GRADUALLY MOVES DOWNWARDLY TOWARD AND THEN THROUGH SAID AGITIATIONZONE AT A RATE CONTROLLED BY SAID SOLIDS WITHDRAWAL RATE, SAID OVERLYINGZONE BEING IN CONTACT WITH SAID AGITATION ZONE.
 2. The method of claim 1further including crushing the ore to top size of about - 3/8 inch andsupplying the ore so crushed for introduction to the vessel withoutfurther subdivision or classification.
 3. The method of claim 1 furtherincluding the steps of removing the leaching liquor from said vesselafter recovery of the values, washing the solids to recover the residualleaching liquor, subsequently removing the washed solids by introducinga liquid as a high velocity jet stream in the lowermost region in thevessel to thereby pulp the solids into a pumpable slurry, andcontinuously removing said slurry as formed from the vessel.
 4. Themethod of claim 1 further including the steps of removing the leachingliquid from the vessel when the mineral values have been recovered toleave at least partially depleted solids in the vessel, and subsequentlyremoving the solids by directing a liquid jet stream into the lowermostregion of the vessel and progressively moving said jet stream, theimpact of the stream causing formation of a flowable slurry of saidsolids, and simultaneously removing freshly formed slurry continuouslythrough the bottom of said vessel.
 5. The method of claim 1 furtherincluding the additional steps of periodically withdrawing a quantity ofsolids from the bottom of said reactor with a minimum of liquid andperiodically introducing a quantity of gas into the bottom region ofsaid reactor, said gas rising upwardly through said vessel to therebyagitate the bed of material contained therein.
 6. The method of claim 1in which the height of said continuous solids bed is maintained at apredetermined level so that the bed fills the major portion of thereaction vessel.
 7. The method of claim 6 Together with the step ofautomatically controlling the height at said predetermined level byproviding an overlying ore supply with gravity feed and choking saidsupply at said level.
 8. The method of claim 1 in which the rotatingagitating stream sweeps progressively radially outwardly from a verticalaxis.
 9. The method of claim 6 in which the rate of solids withdrawal iscontrolled by use of a discharge volume determining pipe having an inletvalve and outlet valve, comprising the additional steps of opening saidinlet valve with said outlet valve in a closed position to load saidpipe section, subsequently closing said inlet valve and opening saidoutlet valve to discharge a predetermined quantity of solids, andrepeating said additional steps in sequence to periodically fill andempty the pipe section.